Tailoring Medium and High-Entropy Perovskite Oxides via Thermal Plasma for Efficient Water Splitting

The rational design of bifunctional electrocatalysts for overall water splitting represents a critical strategy for sustainable energy conversion, addressing one of the most urgent challenges in clean energy technologies. In this work, medium-entropy oxide (MEO) (La0.5 Sr0.5)(Co0.5 Fe0.5)O3 and high-entropy oxide (HEO) (La0.333 Gd0.333 Sr0.333)(Co0.5 Fe0.5)O3 were synthesized through a DC nontransferred arc thermal plasma route, representing the demonstration of entropy-stabilized oxide formation through this rapid and high-temperature approach. The as-synthesized materials were systematically characterized to elucidate their crystal structure, morphology, optical band gap, and oxidation states using a comprehensive suite of spectroscopic and microscopic techniques. Electrochemical evaluation in 1 M KOH revealed that the HEO catalyst exhibits superior bifunctional activity, delivering overpotentials as low as 250 mV for the oxygen evolution reaction (OER) and 128 mV for the hydrogen evolution reaction (HER) at 10 mA cm–2. A two-electrode device assembled with HEO as both anode and cathode required only 1.54 V to achieve 10 mA cm–2, demonstrating its high catalytic activity and operational stability under the measured conditions. These findings not only establish thermal plasma synthesis as a rapid and scalable pathway for entropy-engineered oxides but also demonstrate the promise of HEOs as high-performance electrocatalysts for sustainable hydrogen production.